Hello! Friends,
I am using Qwt plugin with Qt4.3.4 in WinXP to design a GUI. Now i have created a Widget in Qt, added QwtPlot Widget to it named sampleqwtPlot and coded the following files: -

########sampleplot.h##########
Qt Code: 
  1. #ifndef SAMPLEPLOT_H
  2. #define SAMPLEPLOT_H
  3.  
  4. #include<QtGui>
  5. #include <qwt_plot.h>
  6. #include <qwt_plot_curve.h>
  7.  
  8. #include "ui_sampleplot.h"
  9.  
  10. const int PLOT_SIZE = 101;     
  11.  
  12. class samplePlot : public QWidget, private Ui::sampleForm
  13. {
  14.     Q_OBJECT
  15.  
  16. public:
  17. 	samplePlot(QWidget* parent = 0);
  18.  
  19. private:
  20. 	// Arrays holding the values.
  21. 	double xval[PLOT_SIZE];
  22. 	double yval[PLOT_SIZE];
  23. 	// Insert new curve
  24. 	QwtPlotCurve *curve;
  25. };
  26.  
  27. #endif
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########sampleplot.cpp########
Qt Code: 
  1. #include <QtGui> 
  2. #include "sampleplot.h"
  3.  
  4. samplePlot::samplePlot( QWidget *parent )
  5. : QWidget( parent )
  6. {
  7. 	setupUi(this); // this sets up GUI
  8. 	connect( startPushButton, SIGNAL( clicked() ), this, SLOT( draw_curve() ) ); 
  9.  
  10. 	// Axis 
  11. 	sampleqwtPlot->setAxisTitle(QwtPlot::xBottom, "Time/seconds");
  12. 	sampleqwtPlot->setAxisScale(QwtPlot::xBottom, 0, 100);
  13.  
  14. 	sampleqwtPlot->setAxisTitle(QwtPlot::yLeft, "Values");
  15. 	sampleqwtPlot->setAxisScale(QwtPlot::yLeft, 0, 50);
  16.  
  17.         // Set curve styles
  18. 	curve->setPen(QPen(Qt::red));
  19.  
  20. 	//
  21. 	// Calculate values
  22. 	//
  23. 	for(int i=0;i<PLOT_SIZE;i++)
  24. 	{
  25. 		xval[i] = i;
  26. 		yval[i] = 0.5*i;
  27. 	}
  28. 	//
  29. 	//Assign values to the curve.
  30. 	//            
  31. 	curve->setData( xval, yval,  PLOT_SIZE );
  32. 	//        
  33. 	//Attach the curve.
  34. 	//
  35. 	curve->attach( sampleqwtPlot );
  36. 	//
  37. 	// finally, refresh the plot
  38. 	//
  39. 	sampleqwtPlot->replot();
  40. }
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I am able to get the sampleplot.exe file but its not working, like whenever i try to run it, displays error "encountered a problem".

I think i am making a small silly mistake somewhere.

Can anyone please help me out.--> I will be obliged